The long term goal of this research program is to evaluate the relation between the auditory spatial mechanism and the processes by which other, frontally orientated, exteroceptive sensory systems perform their function. The acoustic system is ideally situated to direct charges in the position of the head and eyes. It the only sensory system which has the capacity to provide information about the position of remote events regardless of where the observer is currently facing. There are two specific goals reflected in the current proposal: (1) to determine the capacity of human observers to discrimination and the location of events which occur outside of the visual field; and (2) to assess their capacity to use this information to coordinate changes in head and eye position. Psychophysical discrimination tasks, using a single interval forced choice paradigm, will be employed to assess the subjects capacity to discriminate the location of sound sources on the front-back and vertical dimensions. Both static and moving sources and static and moving subjects will be tested. The second phase of experimentation will examine movements of both the subject's head and eyes while attempting to locate the position of a source. Particular attention will be given to this task when the source is located outside of the subject's field of view. Such research clearly has implication for a wide range of problems whether it be the potential limitations of the unilaterally deaf, pedestrian/industrial safety or the optimal utilization of complex visual arrays.